[PATCH] MINOR: Add sample fetch to detect Supported Elliptic Curves Extension (no replies)

Clients that support ECC cipher suites SHOULD send the specified extension
within the SSL ClientHello message according to RFC4492, section 5.1. We
can use this extension to chain-proxy requests so that, on the same IP
address, a ECC compatible clients gets an EC certificate and a non-ECC
compatible client gets a regular RSA certificate. The main advantage of this
approach compared to the one presented by Dave Zhu on the mailing list
is that we can make it work with OpenSSL versions before 1.0.2.

Example:
frontend ssl-relay
mode tcp
bind 0.0.0.0:443
use_backend ssl-ecc if { req.ssl_ec_ext 1 }
default_backend ssl-rsa

backend ssl-ecc
mode tcp
server ecc unix@/var/run/haproxy_ssl_ecc.sock send-proxy-v2 check

backend ssl-rsa
mode tcp
server rsa unix@/var/run/haproxy_ssl_rsa.sock send-proxy-v2 check

listen all-ssl
bind unix@/var/run/haproxy_ssl_ecc.sock accept-proxy ssl crt /usr/local/haproxy/ecc.foo.com.pem user nobody
bind unix@/var/run/haproxy_ssl_rsa.sock accept-proxy ssl crt /usr/local/haproxy/www.foo.com.pem user nobody

Signed-off-by: Nenad Merdanovic <nmerdan@anine.io>
---
doc/configuration.txt | 10 ++++
src/payload.c | 123 ++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 133 insertions(+)

diff --git a/doc/configuration.txt b/doc/configuration.txt
index 2206788..00f5998 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -12635,6 +12635,16 @@ rdp_cookie_cnt([name]) : integer (deprecated)
ACL derivatives :
req_rdp_cookie_cnt([<name>]) : integer match

+req.ssl_ec_ext : boolean
+req_ssl_ec_ext : boolean (deprecated)
+ Returns a boolean identifying if client sent the Supported Elliptic Curves
+ Extension as defined in RFC4492, section 5.1. within the SSL ClientHello
+ message. This can be used to present ECC compatible clients with EC certificate
+ and to use RSA for all others, on the same IP address. Note that this only
+ applies to raw contents found in the request buffer and not to contents
+ deciphered via an SSL data layer, so this will not work with "bind" lines
+ having the "ssl" option.
+
req.ssl_hello_type : integer
req_ssl_hello_type : integer (deprecated)
Returns an integer value containing the type of the SSL hello message found
diff --git a/src/payload.c b/src/payload.c
index 9bf2d88..127c38d 100644
--- a/src/payload.c
+++ b/src/payload.c
@@ -56,6 +56,127 @@ smp_fetch_len(const struct arg *args, struct sample *smp, const char *kw, void *
return 1;
}

+/* Returns TRUE if the client sent Supported Elliptic Curves Extension (0x000a)
+ * Mainly used to detect if client supports ECC cipher suites.
+ */
+static int
+smp_fetch_req_ssl_ec_ext(const struct arg *args, struct sample *smp, const char *kw, void *private)
+{
+ int hs_len, ext_len, bleft;
+ struct channel *chn;
+ unsigned char *data;
+
+ chn = ((smp->opt & SMP_OPT_DIR) == SMP_OPT_DIR_RES) ? &smp->strm->res : &smp->strm->req;
+ if (!chn->buf)
+ goto not_ssl_hello;
+
+ bleft = chn->buf->i;
+ data = (unsigned char *)chn->buf->p;
+
+ /* Check for SSL/TLS Handshake */
+ if (!bleft)
+ goto too_short;
+ if (*data != 0x16)
+ goto not_ssl_hello;
+
+ /* Check for SSLv3 or later (SSL version >= 3.0) in the record layer*/
+ if (bleft < 3)
+ goto too_short;
+ if (data[1] < 0x03)
+ goto not_ssl_hello;
+
+ if (bleft < 5)
+ goto too_short;
+ hs_len = (data[3] << 8) + data[4];
+ if (hs_len < 1 + 3 + 2 + 32 + 1 + 2 + 2 + 1 + 1 + 2 + 2)
+ goto not_ssl_hello; /* too short to have an extension */
+
+ data += 5; /* enter TLS handshake */
+ bleft -= 5;
+
+ /* Check for a complete client hello starting at <data> */
+ if (bleft < 1)
+ goto too_short;
+ if (data[0] != 0x01) /* msg_type = Client Hello */
+ goto not_ssl_hello;
+
+ /* Check the Hello's length */
+ if (bleft < 4)
+ goto too_short;
+ hs_len = (data[1] << 16) + (data[2] << 8) + data[3];
+ if (hs_len < 2 + 32 + 1 + 2 + 2 + 1 + 1 + 2 + 2)
+ goto not_ssl_hello; /* too short to have an extension */
+
+ /* We want the full handshake here */
+ if (bleft < hs_len)
+ goto too_short;
+
+ data += 4;
+ /* Start of the ClientHello message */
+ if (data[0] < 0x03 || data[1] < 0x01) /* TLSv1 minimum */
+ goto not_ssl_hello;
+
+ ext_len = data[34]; /* session_id_len */
+ if (ext_len > 32 || ext_len > (hs_len - 35)) /* check for correct session_id len */
+ goto not_ssl_hello;
+
+ /* Jump to cipher suite */
+ hs_len -= 35 + ext_len;
+ data += 35 + ext_len;
+
+ if (hs_len < 4 || /* minimum one cipher */
+ (ext_len = (data[0] << 8) + data[1]) < 2 || /* minimum 2 bytes for a cipher */
+ ext_len > hs_len)
+ goto not_ssl_hello;
+
+ /* Jump to the compression methods */
+ hs_len -= 2 + ext_len;
+ data += 2 + ext_len;
+
+ if (hs_len < 2 || /* minimum one compression method */
+ data[0] < 1 || data[0] > hs_len) /* minimum 1 bytes for a method */
+ goto not_ssl_hello;
+
+ /* Jump to the extensions */
+ hs_len -= 1 + data[0];
+ data += 1 + data[0];
+
+ if (hs_len < 2 || /* minimum one extension list length */
+ (ext_len = (data[0] << 8) + data[1]) > hs_len - 2) /* list too long */
+ goto not_ssl_hello;
+
+ hs_len = ext_len; /* limit ourselves to the extension length */
+ data += 2;
+
+ while (hs_len >= 4) {
+ int ext_type, ext_len;
+
+ ext_type = (data[0] << 8) + data[1];
+ ext_len = (data[2] << 8) + data[3];
+
+ if (ext_len > hs_len - 4) /* Extension too long */
+ goto not_ssl_hello;
+
+ /* Elliptic curves extension */
+ if (ext_type == 10) {
+ smp->type = SMP_T_BOOL;
+ smp->data.uint = 1;
+ return 1;
+ }
+
+ hs_len -= 4 + ext_len;
+ data += 4 + ext_len;
+ }
+ /* server name not found */
+ goto not_ssl_hello;
+
+ too_short:
+ smp->flags = SMP_F_MAY_CHANGE;
+
+ not_ssl_hello:
+
+ return 0;
+}
/* returns the type of SSL hello message (mainly used to detect an SSL hello) */
static int
smp_fetch_ssl_hello_type(const struct arg *args, struct sample *smp, const char *kw, void *private)
@@ -639,6 +760,7 @@ static struct sample_fetch_kw_list smp_kws = {ILH, {
{ "rdp_cookie_cnt", smp_fetch_rdp_cookie_cnt, ARG1(0,STR), NULL, SMP_T_UINT, SMP_USE_L6REQ },
{ "rep_ssl_hello_type", smp_fetch_ssl_hello_type, 0, NULL, SMP_T_UINT, SMP_USE_L6RES },
{ "req_len", smp_fetch_len, 0, NULL, SMP_T_UINT, SMP_USE_L6REQ },
+ { "req_ssl_ec_ext", smp_fetch_req_ssl_ec_ext, 0, NULL, SMP_T_BOOL, SMP_USE_L6REQ },
{ "req_ssl_hello_type", smp_fetch_ssl_hello_type, 0, NULL, SMP_T_UINT, SMP_USE_L6REQ },
{ "req_ssl_sni", smp_fetch_ssl_hello_sni, 0, NULL, SMP_T_STR, SMP_USE_L6REQ },
{ "req_ssl_ver", smp_fetch_req_ssl_ver, 0, NULL, SMP_T_UINT, SMP_USE_L6REQ },
@@ -648,6 +770,7 @@ static struct sample_fetch_kw_list smp_kws = {ILH, {
{ "req.payload_lv", smp_fetch_payload_lv, ARG3(2,UINT,UINT,SINT), val_payload_lv, SMP_T_BIN, SMP_USE_L6REQ },
{ "req.rdp_cookie", smp_fetch_rdp_cookie, ARG1(0,STR), NULL, SMP_T_STR, SMP_USE_L6REQ },
{ "req.rdp_cookie_cnt", smp_fetch_rdp_cookie_cnt, ARG1(0,STR), NULL, SMP_T_UINT, SMP_USE_L6REQ },
+ { "req.ssl_ec_ext", smp_fetch_req_ssl_ec_ext, 0, NULL, SMP_T_BOOL, SMP_USE_L6REQ },
{ "req.ssl_hello_type", smp_fetch_ssl_hello_type, 0, NULL, SMP_T_UINT, SMP_USE_L6REQ },
{ "req.ssl_sni", smp_fetch_ssl_hello_sni, 0, NULL, SMP_T_STR, SMP_USE_L6REQ },
{ "req.ssl_ver", smp_fetch_req_ssl_ver, 0, NULL, SMP_T_UINT, SMP_USE_L6REQ },
--
2.1.4